Air-fuel mixture supply control system for use with carburetors for internal combustion engines

ABSTRACT

An electronic system for controlling a carburetor to supply an air-fuel mixture to an internal combustion engine at an optimum air-fuel ratio under all continuously variably conditions of engine speed, engine temperature, throttle opening and atmospheric pressure.

United States Patent Masaki et al.

[ Jan. 21, 1975 AIR-FUEL MIXTURE SUPPLY CONTROL SYSTEM FOR USE WITHCARBURETORS FOR INTERNAL COMBUSTION ENGINES Inventors: Kenji Masaki,Yokohama; Shigeo Aono, Yokosuka, both of Japan Assignee: Nissan MotorsCompany, Limited,

Yokohama, Japan Filed: Apr. 13, 1973 Appl. No.: 351,009

Foreign Application Priority Data Apr. 14, 1972 Japan 47-37457 US. Cl.123/119 R, 123/32 EA, 123/106, 123/139 AW Int. Cl. F02d 35/00, F02b15/00, F02d 33/00 Field of Search... 123/119 R, 32 EA, 139 AW, 123/100,106

[56] References Cited UNITED STATES PATENTS 3,470,858 10/1969 Mycroft[23/139 AW 3,548,792 12/1970 Palmerv 123/[19 R X 3,727,591 4/1973 Sudzi123/119 R X 3,745,768 7/1973 Zcchnzill et ail. 123/119 R X 3,750,6328/1973 Zechnull 123/12 liA 3,756,208 9/1973 Todu ct all 123/119 R XPrimary Examiner-Charles J. Myhrc Assistant Examiner-Tony Argenbright[57] ABSTRACT An electronic system for controlling a carburetor tosupply an air-fuel mixture to an internal combustion engine at anoptimum air-fuel ratio under all continuously variably conditions ofengine speed. engine temperature, throttle opening and atmosphericpressure,

24 Claims, 13 Drawing Figures Patented Jan. 21, 1975 3,861,366

6 Sheets-Sheet l 4 44 n L Q ,2 48

ELECTRONIC 5O 42 COMPUTING v CIRCUIT 45 Susi) ELECTRONIC CONTROPatefnted Jan. 21, 1975 6 Sheets-Sheet 2 mOlzmmzmo ZOiUZDm moZwmzmoZOEUZDm @2250 fiiomg ZOCOZDu m ammam mzazm Patented Jan. 21, 19753,861,366

6 Sheets-Sheet 5 F g. 4 5| 2 6 g 3: I L1. Z J O: Q S g m Lu 2 [l 2 E 4 WI 2 LL! UJ Q E z 6 5 L9 2 L T f 5 E ENGINE SPEED ENGINE TEMPERATUREANALOG SIGNAL Il ANALOG SIGNAL i [-79 5 F/ Y 6 S Ii :4 0 8 1 BE 9 [L U)v /1/ O gJ 1 LLJZ Lil 2E v P9 97 Q I H E? I E5 Ea THROTTLE OPENING 760mmHg ATMOSPHERIC PRESSURE vANA SIGNAL Q ANALOG SIGNAL 3 Patented Jan. 21,1975 s Sheets-Sheet 4:

Patented Jan. 21, 1975 6 Sheets-Sheet 5 M959 wuzwmmmwm F J w w I I I III F m L l llllmpli M IHWM MWHH UWIMI M I L s H M KI I l l l l l v w IIiiH 31min mom 2 329m ZZQCZE b F AIR-FUEL MIXTURE SUPPLY CONTROL SYSTEMFOR USE WITH CARBURETORS FOR INTERNAL COMBUSTION ENGINES The presentinvention relates generally to carburetors for internal combustionengines of motor vehicles and, more particularly, to an air-fuel mixturesupply control system for electronically controlling a carburetor tosupply an air-fuel mixture to an internal combustion engine at anoptimum air-fuel ratio under variable engine operating conditions.

Unburned hydrocarbons in engine exhaust gases are significant for twomajor reasons: they are causes of air pollution, and they indicate poorfuel burning efficiency. For the purpose of eliminating or minimizingunburned hydrocarbons in exhaust gases, many attempts have been made tooptimize the air-fuel ratio of the air-fuel mixture being supplied to aninternal combustion engine. However, many difficulties have beenencountered in prior art methods in maintaining the air-fuel mixture atan optimum air-fuel ratio under the widely varying operating conditionsof a motor vehicle.

As is well known in the art, it has been customary to incorporate into acarburetor an automatic choke mechanism which meters intake air inresponse to variations in engine temperature. However, since anautomatic choke is responsive to variations in engine temperature only,it has also been customary to incorporate into a carburetor a system offuel jets and air bleeds of fixed crosssectional areas, in a furtherattempt to provide a proper air-fuel ratio corresponding to varyingengine operating conditions such as idling, acceleration, decelerationand cruising. However, it is to be appreciated that these prior artdevices are only approximately effective in adjusting the air-fuel ratioto an optimum value in response to subtle variations in engine speed,engine temperature, throttle opening and atmospheric pressure.

The lack of precision and efficiency of prior art airfuel mixture supplycontrol systems is a direct cause of not only poor fuel economy, butalso air pollution caused by unburned hydrocarbons contained in exhaustgases emitted from internal combustion engines. Thus, there is apressing need for an air-fuel mixture supply control system which willsupply an air-fuel mixture to an internal combustion engine at anoptimum air-fuel ratio under all operating conditions of the engine, andthus reduce to a minimum the undesirable effects of poor fuel economyand air pollution.

It is accordingly a principal object of the present invention to providean air-fuel mixture supply control system for a carburetor of a motorvehicle, which system is capable of electronically controlling thecarburetor to supply an air-fuel mixture to an internal combustionengine at an optimum air-fuel ratio under all engine operatingconditions.

It is another object of the present invention to provide an air-fuelmixture supply control system which is capable of eliminating orminimizing air pollution caused by the presence of unburned hydrocarbonsin engine exhaust gases, and simultaneously provide increased fueleconomy in operating an internal combustion engine due to increasedcombustion efficiency.

It is still another object of the present invention to provide anair-fuel mixture supply control system which is highly reliable inoperation and can easily be installed on an existing carburetor.

It is a further object of the present invention to provide an air-fuelmixture supplycontrol system which is capable of improving thedriveability of the motor vehicle.

It is still a further object of the present invention to provide anair-fuel mixture supply control system which is capable of prolongingthe expected life span of an exhaust gas cleaner incorporated in a motorvehicle.

An air-fuel mixture supply control system in accordance with the presentinvention controls a carburetor of an internal combustion engine tosupply an air-fuel mixture to the engine at an optimum air-fuel ratiounder all engine operating conditions by sensing the engine speed,engine temperature, throttle opening and atmospheric pressure by meansof appropriate sensors, producing an electronic functional signalrepresenting an optimum mixture air-fuel ratio corresponding to theabove mentioned sensed conditions in an electronic computing circuit,transforming the electronic functional signal into an electronicoperating signal in an electronic control circuit, and applying theelectronic operating signal to an actuating mechanism which eitheradjusts the flow of air entering the carburetor or adjusts the flow offuel passing through a metering section of the carburetor in response tothe received electronic operating signal.

These and other objects and advantages of the present invention wilbecome apparent from the following detailed description taken inconjunction with the accompanying drawings in which like referencenumerals designate corresponding parts in all figures and in which:

FIG. 1 is a schematic sectional view of an overall configuration of anair-fuel mixture supply control system according to the presentinvention and a carburetor controlled thereby;

FIG. 2 is a schematic block diagram of a preferred embodiment of anelectronic computing circuit and an electronic control circuit shown inFIG. 1;

FIG. 3 shows the relationship between an engine speed analog signal andan electronic functional signal produced therefrom;

FIG. 4 shows the relationship between an engine temperature analogsignal and an electronic functional signal produced therefrom;

FIG. 5 shows the relationship between a throttle opening analog signaland an electronic functional signal produced therefrom;

FIG. 6 shows the relationship between an atmospheric pressure analogsignal and an electronic functional signal produced therefrom;

FIG. 7 shows an example of a function generator shown in FIG. 2;

FIG. 8 shows another example of a function generator shown in FIG. 2;

FIG. 9 shows an example of an electronic functional signal representingan optimum air-fuel ratio of an airfuel mixture being supplied to aninternal combustion engine as a function of time;

FIG. 10 is a schematic block diagram of another preferred embodiment ofan electronic computing circuit and an electronic control circuit shownin FIG. 1;

FIG. 11 shows an example of an electric dither signal to be fed into asumming circuit shown in FIG. 10;

FIG. 12 shows an example of an electronic signal in which an electricdither signal shown in FIG. 11 is combined with an electronic functionalsignal shown in FIG. 9; and

FIG. 13 shows an example of an electric pulse width signal produced fromthe electronic signal shown in FIG. 12 by the comparator shown in FIG.10.

Referring more particularly to FIG. 1, there is shown an air-fuelmixture supply control system of the present invention and a carburetorcontrolled thereby, the carburetor being generally indicated by areference numeral 10. The carburetor 10 comprises a carburetor body 11,the inner surface of which defines a carburetor induction passage 12communicating with an intake manifold of an internal combustion engine(not shown). The carburetor 10 is also provided with a throttle valve 13which is fixedly mounted on a rotatable shaft 13a for rotation in thecarburetor induction passage 12, a venturi 14, a fuel mixing systemgenerally designated by a numeral 15, a float chamber 16 containing andsupplying fuel 16a into the fuel mixing system l5 therefrom, and a chokevalve 17 which is fixedly mounted on a rotatable shaft 17a for rotationin the carburetor induction passage 12. The carburetor body 11 hasfurther formed therein an air-fuel mixing chamber 18 which is disposedin the fuel mixing system 15, a main air supply passage 19 and anauxiliary air supply passage 20 for supplying air into the air-fuelmixing chamber 18 from the ambient atmosphere through air bleed jets 21and 22 respectively which are mounted on the carburetor body 11 and haveopenings 21a and 22a respectively, and a main fuel supply passage 23 forsupplying fuel into the air-fuel mixing chamber 18 from the floatchamber 16 through a main fuel jet 24 which is disposed therein. Themain fuel jet 24 of the main fuel supply passage 23 is bypassed by anauxiliary fuel supply passage 25 which is provided with an auxiliaryfuel jet 26 therein. The fuel mixing system opens into the venturi 14through a nozzle 27 having an opening or port 27a so as to introduceair-fuel mixture from the air-fuel mixing chamber 18 into the carburetorinduction passage 12.

The air bleed jets 21 and 22 are so designed that the effectivecross-sectional areas of their openings 21a and 22a have predeterminedfixed values for effective operation. The fuel jets 24 and 26 also havecrosssectional areas which are predetermined fixed values for effectiveoperation, and fuel introduced through the fuel jets 24 and 26 into theair-fuel mixing chamber 18 is mixed with air introduced therein throughthe air bleed jets 21 and 22. Air-fuel mixture from the air-fuel mixingchamber 18 is sucked into the venturi 14 through the nozzle 27 by vacuumproduced in the venturi 14 by normal operation of the engine. Thus, itis to be appreciated that the amount and air-fuel ratio of airfuelmixture sucked into the venturi l4 and accordingly into the carburetorinduction passage 12 is determined by the effective cross-sectionalareas of the openings 21a and 22a of the air bleed jets 21 and 22, theeffective cross-sectional areas of the fuel jets 24 and 26, the level ofvacuum in the venturi 14, and the difference in height between the port27a of the nozzle 27 and the surface of the fuel 16a in the floatchamber 16 (normally maintained as constant). Accordingly, it may beappreciated that control of the air-fuel ratio of the air fuel mixturebeing supplied into the carburetor induction passage 12 can beaccomplished by varying at least one of the cross-sectional areas of theopenings 21a and 22a of the air-bleed jets 21 and 22 respectively, andthe fuel jets 24 and 26.

An air-fuel ratio control mechanism of the present invention will behereinafter be described for the purpose of example as comprising an airsupply metering device 30 shown in FIG. 1, which controls the amount ofair entering the air bleed jet 21 from the ambient atmosphere by varyingthe effective cross-sectional area at the opening 21a of the air bleedjet 21.

The air supply metering device 30 generally comprises an air flowcontrol valve assembly 31 which is operatively disposed over the opening21a of the air bleed jet 21 for controlling the amount of air enteringthe main air supply passage 19, and an electric actuating device 32 foractuating the air flow control valve assembly 31. The air flow controlvalve assembly 31 comprises a needle valve 33 which has a tapered tip33a projecting into the opening 21a. The tapered tip 33a is operative tomove into the opening 21a to a full or partial extent, and thereby varythe effective crosssectional area at the opening 21a and accordingly theamount of air passing therethrough into the main air supply passage 19.The electric actuating device 32 comprises a stationary core 34 forminga housing 35 which is mounted on the carburetor body 11 by a suitablefastening means such as at least one screw 34a and is provided thereinwith a pair of solenoid coils 34b and 34c which are positioned as facingeach other and a movable core 36 which rockably connected at one endthereof to the housing 35. The movable core 36 is connected at its otherend to the needle valve 33 so as to rockably move the tapered tip 33a ofthe needle valve 33 into the opening 21a of the air bleed jet 21 inresponse to a magnetic force induced in the solenoid coils 34b and 340.i

It is to be appreciated that, although the air supply metering device 30is mounted on the carburetor body 11 so as to vary the effectivecross-sectional area at the opening 21a of the air bleed jet 21 whichopens into the main air supply passage 19, it may be mounted on thecarburetor body 11 so as to vary the effective crosssectional area atthe opening 22a of the air bleed jet 22 which opens into the auxiliaryair supply passage 20, such that the amount of air entering the air-fuelmixing chamber 18 is effectively metered in response to varyingoperating conditions of the engine.

It is further to be appreciated that an air supply metering device 30 ofthis invention as described above may alternatively be embodied as afuel supply metering device 30' which in this case is so arranged as tobe operable to vary the effective cross-sectional area of the auxiliaryfuel jet 26 which is located in the auxiliary fuel supply passage 25,such that the fuel supply metering device 30' shown in FIG. 1 varies theamount of fuel supplied into the air-fuel mixing chamber 18 in responseto varying engine operating conditions.

Moreover, it is to be appreciated that a fuel supply metering device 30'may be alternatively adapted to control the main fuel jet 24 in anessentially similar manner as described above in relation to theauxiliary fuel jet 26.

The fuel supply metering device 30 described above operates andfunctions in an essentially similar manner with the air supply meteringmechanism 30 also previously described so that a detailed explanation ofthe operation of the fuel supply metering device 30' can be dispensedwith.

In order to effectively control the air supply metering device 30 and/orthe fuel supply metering device 30 in response to all operatingconditions of the engine, an air-fuel mixture supply control system-ofthis invention is provided with at least one of an engine speed sensor40 having a gear 41 engaging with a gear 42 which is fixably mounted onan engine driven shaft 43 to produce an electric engine speed pulsesignal which is covered by a converter 44 into an electric engine speedanalog signal n, an engine temperature sensor 45 comprising, forexample, a thermistor which is mounted on the carburetor body 11 toproduce an electric engine temperature analog signal t, a throttleopening sensor 46 comprising, for example, a potentiometer to produce anelectric throttle opening analog signal 0, and an atmospheric pressuresensor 48 comprising, for example, a pressure sensitive element toproduce an atmospheric pressure analog signal p. The electric analogsignals n, t, 0 and p are fed into an electronic computing circuit 50which modifies and combines the analog signals n, t, 6 and p andproduces an electronic functional signal S representing an optimumair-fuel ratio for an air-fuel mixture being supplied into the engine asa function of the above mentioned sensed conditions. The electronicfunctional signal S is fed into an electronic control circuit 60 whichproduces an electronic operating signal S which is fed into the solenoidcoils 34b and 346 of the air supply metering device 30 and/or the fuelsupply metering device 30' for actuation thereof.

FIG. 2 illustrates an embodiment of an electronic computing circuit 50and an electronic control circuit 60 shown in FIG. 1. The computingcircuit 50 generally comprises four function generators 51, 52, 53 and54, and a summing circuit 55. When, in operation, the function generator51 receives an engine speed analog signal it from the engine speedsensor 40 through the converter 44, it produces an electronic functionalsignalfln) which is then fed into the summing circuit 55. Similarly,when the function generator 52 receives an engine temperature analogsignal r from the engine temperature sensor 45, it produces anelectronic functional signal f(t) which is then fed into the summingcircuit 55; when the function generator 53 receives a throttle openinganalog signal 0 from the throttle opening sensor 46, it produces anelectronic functional signalfl6) which is then fed into the summingcircuit 55; and when the function generator 54 receives an atmosphericpressure analog signal p from the atmospheric pressure sensor 48, itproduces an electronic functional signal flp) which is then fed into thesumming circuit 55. The summing circuit 55 upon receiving the functionalsignals f(n),f(t),f(0) and flp) from the respective function generators51, 52, 53 and 54 produces an electronic functional signal S, whichrepresents optimum air-fuel ratio of an airfuel mixture being suppliedinto the internal combustion engine. The electronic functional signal Sis equal to an electronic functional signal ftf) which is obtained fromthe following relation:

The electronic functional signal S is then fed into the electroniccontrol circuit 60 which produces an electronic operating signal S whichis then fed into the air supply metering device 30 and/or the fuelsupply metering mechanism 30, as shown in FIG. 1.

Reference is now made to FIGS. 3 to 6 in which the relationships betweenthe electric analog signals n, t, 6 and p fed into the respectivefunction generator 51, 52, 53 and 54, and the respective electronicfunctional signalsf(n),f(t),f(0) andf(p) produced by the respectivefunction generators is clearly shown. FIG. 3 shows the relationshipbetween an engine speed analog signal n and an electronic functionalsignal fln) produced by the function generator 51 in response thereto.The engine speed analog signal n as represented by a broken line is asignal produced by the converter 44 in response to a received enginespeed pulse signal generated by the engine speed sensor 40 andrepresents the engine speed. The function generator modifies the enginespeed analog signal n to produce an electronic functional signal f(n),an example of which is represented by a solid line.

FIG. 4 shows the relationship between an engine temperature analogsignal I and an electronic functional signal f(z) produced therefrom.The engine temperature analog signal t represented by a broken line isfed from the engine temperature sensor 45 into the function generator 52which then produces the electronic functional signal f(t), an example ofwhich is represented by a solid line. The functional signal flz)represents an optimum air-fuel ratio of an air-fuel mixture beingsupplied into the engine in response to the sensed engine temperature.

FIG. 5 shows the relationship between a throttle opening analog signal 6and an electronic functional signal f(6) produced therefrom. Thethrottle opening analog signal 0 as represented by a broken line is fedfrom the throttle opening sensor 46 into the function generator 53 whichthen produces an electronic functional signal f(6) an example of whichis represented by a solid line. The functional signal f(6) represents anoptimum air'fuel ratio of an air-fuel mixture being supplied into theengine in response to the sensed throttle opening.

FIG. 6 shows the relationship between an atmospheric pressure analogsignal p as represented by a broken line which is fed from theatmospheric pressure sensor 48 into the function generator 54 which thenproduces an electronic functional signal f(p), an example of which isrepresented by a solid line. The functional signal f(p) represents anoptimum air-fuel ratio of an air-fuel mixture being supplied into theengine at the sensed atmospheric pressure.

Examples of circuit arrangements of the function generators employed inthe invention are shown in FIGS. 7 and 8. In FIG. 7, the functiongenerator generally comprises a functional amplifier 56, a resistor 57connected between the input and output terminals of the functionalamplifier 56, and a diode 58. A function generator of this configurationmay be utilized for producing an electronic functional signal inresponse to a received engine speed analog signal n, an enginetemperature analog signal 2, or a throttle opening analog signal 0. InFIG. 8, a function generator comprises an functional amplifier 56' and aresistor 57 and diode 58' connected in electrical series with each otherbetween the input and output terminals of the functional amplifier 56'.A function generator of this configuration may be utilized for producingan electronic functional signal in response to a received atmosphericpressure analog signal p.

As mentioned above, the electronic functional signals f(n),f(t),f() andf(p) generated by the function generators 51, 52, 53 and 54 respectivelyare fed into the summing circuit 55 in which the functional signals arecombined. The summing circuit 55 then produces an electronic functionalsignal S f( as shown in FIG. 9. The functional signal S is then fed intothe electronic control circuit 60 in which the signal is transformedinto an electronic operating signal S The operating signal S is suppliedto the air supply metering device 30 and/or the fuel supply meteringdevice 30' for actuation thereof, such that the air-fuel ratio of theairfuel mixture being supplied to the engine is continuously adjusted toan optimum value in response to the sensed combination of engineoperating conditions.

FIG. illustrates another embodiment of an electronic computing circuit50 and an electronic control circuit 60 shown in FIG. 1. In thisembodiment, a summing circuit 55' receives an electric dither signal Sdsuch as triangular signal which is produced by a dither signal generator(not shown) as illustrated in FIG. 11 in addition to the functionalsignals f(n),f(t),f(0) and f(p), and produces an electronic functionalsignal S, which is equal to an electronic functional signal F'U), anexample of which is shown in FIG. 12. The functional signal F'(f) isproduced by combining the dither signal Sd and the functional signal S,as shown in FIG. 9. The functional signal F '(f) is fed into anelectronic control circuit 60 comprising a comparator 61 to which areference voltage signal 8,; as shown in FIG. 12 is supplied from areference voltage signal generator (not shown), and an amplifier 62. Thecomparator 61 produces an electric pulse width signal S, in response tothe reference voltage signal 8,; and the input functional signal F'(f),an example of which is shown in FIG. 13. This pulse width signal S, isfed into the amplifier 62 in which it is amplified. The output signalfrom the amplifier 62 is an electronic operating signal 8' and is fedinto the air supply metering device 30 and/or the fuel supply meteringdevice 30'. The air supply metering device 30, for example, is actuatedby the operating signal S; in such a way that the tapered tip 33a of theneedle valve 33 is moved into the opening 21a of the air bleed jet 21,for example, so as to completely or partially close the opening 21a whenthe operating signal S: has an instantaneous positive polarity or ONstate, and is moved out of the opening 21a when the operating signal Shas an instantaneous negative polarity or OFF" state, as shown in FIG.13. Thus, it can be seen that the proportion of time the opening 21a isclosed by the tapered tip 33a of the,needle valve 33 is determined bythe proportion of time the operating signal S' has a positive polarityor ON state, and that the proportion of time the opening 21a is coveredand consequently the amount of air passing into the main air supplypassage 19 can be continuously varied by varying the pulse widths of thepulses of the operating signal S' Since the widths of the pulses of theoperating signal 8' are determined by the reference voltage signal S andthe functional signal S which is in turn determined by the sensed engineoperating conditions, it can be appreciated that this embodiment of thepresent invention effectively controls a carburetor of an internalcombustion engine to provide an optimum air-fuel mixture under allengine operating conditions by alternately opening and closing an airbleed intake port of the carburetor at a ratio determined by sensedoperating conditions of the engine.

In this embodiment, any problems which might be encountered due tofriction or hysteres is in the air supply metering device 30 and/or thefuel supply metering device 30 respectively are effectively eliminatedby controlling the air supply metering device 30 and/or the fuel supplymetering device 30 respectively in an on-off manner.

The herein presented detailed descriptions of preferred embodiments ofthe present invention are for the purpose of explaining the principlesthereof only, and are not to be considered as limiting or restrictingthe present invention, since many modifications may be made by exerciseof skill in the art without departing from the scope of the presentinvention.

What is claimed is: 1. In a carburetor for an internal combustion enginehaving air and fuel supplying means which include mixing means formixing air and fuel, at least one air supply passageway and a main fuelsupply passageway for supplying air and fuel respectively into saidmixing means, said at least one air supply passageway being incommunication with the ambient atmosphere, a fuel supply reservoir forsupplying fuel into said main fuel supply passageway, a flow controlmeans operatively disposed in said main fuel supply passageway, anair-fuel mixture supply passageway for supplying air-fuel mixture fromsaid mixing means into an induction passage of said carburetor,throttling means operatively disposed in said induction passage forcontrolling the amount of said air-fuel mixture being supplied into saidengine, an auxiliary fuel supply passageway bypassing said flow controlmeans of said main fuel supply passageway, flow control meansoperatively disposed in said auxiliary fuel supply passageway, and anair bleed jet mounted on said carburetor and communicating between theambient atmosphere and said air and fuel supplying means; an air-fuelmixture supply control system which comprises:

electronic computing means responsive to at least one of electricsignals representing prevailing values of engine operating conditionsincluding engine speed, engine temperature, throttle opening andatmospheric pressure to produce an electric output signal representingan optimum air-fuel ratio of said air-fuel mixture and corresponding atall times to prevailing engine operating conditions;

electronic control means responsive to said output signal from saidelectronic computing means to produce an electric operating signal; and

an air supply metering device which is actuated by said operating signalfrom said electronic control means to meter a flow of air being passedthrough said air supply passageway from the ambient atmosphere.

2. In a carburetor as claimed in claim 1, said electronic computingmeans comprising at least one function generator responsive to at leastone of said electric signals representing said engine operatingconditions to produce at least one electronic functional signaltherefrom, and summing means responsive to said at least one functionalsignal to produce said electric output signal representing said optimumvalue of the air-fuel ratio of said air-fuel mixture.

3. In a carburetor as claimed in claim 2, said electronic control meanscomprising an amplifier for amplifying said electric output signal fromsaid summing means to produce said electric operating signal to be fedinto said air-fuel mixture supply control system.

4. In a carburetor as claimed in claim 1, said air supplying meteringdevice comprising an air flow control valve assembly which isoperatively disposed over an opening of said air bleed jet for meteringthe amount of air being passed into said air supply passageway, and anelectric actuating device for actuating said air flow control valveassembly in response to said operating signal from said electroniccontrol means.

5. In a carburetor as claimed in claim 4, said electric actuating devicecomprising a stationary core forming a housing which is mounted on saidcarburetor and is provided with a pair of solenoid coils therein, and arockable movable core which is rockably connected at one end to saidhousing and the other end of which is rockably moved in or out of saidopening of said air bleed jet in response to a magnetic force induced insaid solenoid coils.

6. In a carburetor as claimed in claim 5, said air flow control valveassembly comprising a valve needle with a tapered end which projectsinto said opening of said air bleed jet and is fixedly attached to saidother end of said movable core, said tapered end being capable ofvarying the effective cross-sectional area of said opening of said airbleed jet to thereby meter the amount of air being supplied into saidair supply passageway from the ambient atmosphere.

7. In a carburetor for an internal combustion engine having air and fuelsupplying means which include mixing means for mixing air and fuel, atleast one air supply passageway and a main fuel supply passageway forsupplying air and fuel respectively into said mixing means, said atleast one air supply passageway being in communication with the ambientatmosphere, a fuel supply reservoir for supplying fuel into said mainfuel passageway, flow control means operatively disposed in said mainfuel supply passageway, an air-fuel mixture supply passageway forsupplying air-fuel mixture from said mixing means into an inductionpassage of said carburetor, throttling means operatively disposed insaid induction passageway for controlling the amount of said air-fuelmixture being supplied into said engine, an auxiliary fuel supplypassageway bypassing said flow control means of said main fuel supplypassageway, flow control means operatively disposed in said auxiliaryfuel supply passageway, and an air bleed jet mounted on said carburetorand communicating between the ambient atmosphere and said air and fuelsupplying means; an air-fuel mixture supply control system whichcomprises:

electronic computing means responsive to at least one of electricsignals representing prevailing values of engine operating conditionsincluding engine speed, engine temperature, throttle opening andatmospheric pressure to produce an electric output signal representingan optimum air-fuel ratio of said airfuel mixture corresponding at alltimes to prevailing engine operating conditions;

electronic control means responsive to said output signal from saidelectronic computing means to produce an electric operating signal; and

a fuel supply metering device which is actuated by said operating signalfrom said electronic control means to meter a flow of fuel beingsupplied into said air and fuel mixing means through said auxiliary fuelsupply passageway from said fuel supply reservoir.

8. In a carburetor as claimed in claim 7, said electronic computingmeans comprising at least one function generator responsive to at leastone of said electric signals representing said engine operatingconditions to produce at least one electronic functional signaltherefrom, and summing means responsive to said at least one functionalsignal to produce said electric output signal representing said optimumvalue of the air-fuel ratio of said air-fuel mixture.

9. In a carburetor as claimed in claim 8, said electronic control meanscomprising an amplifier for amplifying said electric output signal fromsaid summing means to produce electric operating signal to be fed intosaid air-fuel mixture supply control system.

10. In a carburetor as claimed in claim 8, said fuel supply meteringdevice comprising a fuel flow control valve assembly which isoperatively disposed in said auxiliary fuel supply passageway, and anelectric actuating device for a actuating said fuel flow control valveassembly in response to said operating signal from said electroniccontrol means for metering the amount of fuel being supplied into saidair and fuel mixing means through said auxiliary fuel supply passagewayfrom said fuel supply reservoir.

11. In a carburetor as claimed in claim 10, said electric actuatingdevice comprising a stationary core forming a housing which is providedwith a pair of solenoid coils therein, and a rockable movable core whichis rockably connected at one end to said housing and the other end ofwhich is rockably actuated by a magnetic force induced in said solenoidcoils by said electric operating signal from said electronic controlmeans.

12. In a carburetor as clained in claim 11, said fuel flow control valveassembly being operatively disposed in said auxiliary fuel supplypassageway and operatively connected to and actuated by said other endof said movable core of said electric actuating device to meter theamount of fuel being supplied into said air and fuel mixing meansthrough said auxiliary fuel supply passageway from said fuel supplyreservoir in response to said electric operating signal from saidelectronic control means.

13. In a carburetor for an internal combustion engine having air andfuel supplying means which include mixing means for mixing air and fuel,at least one air supply passageway and a main fuel supply passageway forsupplying air and fuel respectively into said mixing means, said atleast one air supply passageway being in communication with the ambientatmosphere, a fuel supply reservoir for supplying fuel into said mainfuel supply passageway, an air-fuel mixture supply passageway forsupplying air-fuel mixture from said mixing means into an inductionpassage of said carburetor, throttling means operatively disposed insaid induction passageway for controlling the amount of said air-fuelmixture being supplied into said engine, an air bleed jet communicatingbetween the ambient atmosphere and said air and fuel supplying means,flow control means operatively disposed in said main fuel supplypassageway, an auxiliary fuel supply passageway bypassing said flowcontrol means of said main fuel supply passageway, and a flow controlmeans operatively disposed in said auxiliary fuel supply passageway; anair-fuel mixture supply control system which comprises:

electronic computing means responsive to an electric dither signal andat least one of electric signals representing prevailing values ofengine operating conditions including engine speed, engine temperature,throttle opening and atmospheric pressure to produce an electric outputsignal representing an optimum air-fuel ratio of said air-fuel mixtureand corresponding at all times to prevailing engine operatingconditions;

electronic control means responsive to said output signal from saidelectronic computing means to produce an electric operating pulse widthsignal; and

an air supply metering device which is actuated by said operating pulsewidth signal from said electronic control means to meter the flow of airpassing through said at least one air supply passageway from the ambientatmosphere.

14. In a carburetor as claimed in claim 13, said electronic computingmeans comprising at least one function generator responsive to at leastone of said electric signals representing said engine operatingconditions to produce at least one electronic functional signaltherefrom, and summing means responsive to said at least one functionalsignal and said dither signal to produce said electric output signalrepresenting said optimum air-fuel ratio of said air-fuel mixture.

15. In a carburetor as claimed in claim 14, said electronic controlmeans comprising a comparator responsive to said electric output signalfrom said summing means to produce an electric pulse width signal, andan amplifier for amplifying said pulse width signal to produce saidoperating pulse width signal to be fed into said air-fuel mixture supplycontrol system.

16. In a carburetor as claimed in claim 13, said air supply meteringdevice comprising an air flow control valve assembly which isoperatively disposed over an opening of said air bleed jet for meteringthe amount of air being passed into said air supply passageway, and anelectric actuating device for actuating said air flow control valveassembly in response to said operating pulse width signal from saidelectronic control means.

17. In a carburetor as claimed in claim 16, said electric actuatingdevice comprising a stationary core forming a housing which is mountedon said carburetor and is provided with a pair of solenoid coilstherein, and a rockable movable core which is rockably connected at oneend to said housing and the other end of which is rockably moved in orout of said opening of said air bleed jet in response to a magneticforce induced in said solenoid coils.

18. In a carburetor as claimed in claim 17, said air flow control valveassembly comprising a valve needle with a tapered end which projectsinto said opening of said air bleed jet and is fixedly attached to saidother end of said movable core, said tapered end being capable ofopening and closing said opening of said air bleed jet to meter theamount of air passing into said air supply passageway from the ambientatmosphere.

19. In a carburetor for an internal combustion engine having air andfuel supplying means which include mixing means for mixing air and fuel,at least one air supply passageway and a main fuel supply passageway forsupplying air and fuel respectively into said mixing means, said atleast one air supply passageway being in communication with the ambientatmosphere, a fuel supply reservoir for supplying fuel into said mainfuel supply passageway, flow control means operatively disposed in saidmain fuel supply passageway, an air-fuel mixture supply passageway forsupplying air-fuel mixture from said mixing means into an inductionpassage of said carburetor, throttling means operatively disposed insaid induction passage for controlling the amount of said air-fuelmixture being supplied into said engine, an auxiliary fuel supplypassageway bypassing said flow control means of said main fuel supplypassageway, flow control means operatively disposed in said auxiliaryfuel supply passageway, and an air bleed jet mounted on said carburetorand communicating between the ambient atmosphere and said air and fuelsupplying means; an air-fuel mixture supply control system whichcomprises:

electronic computing means responsive to an electric dither signal andat least one of electric signal representing prevailing values of engineoperating conditions including engine speed, engine temperature,throttle opening and atmospheric pressure to produce an electric outputsignal representing an optimum air-fuel ratio of said air-fuel mixtureand corresponding at all times to prevailing engine operatingconditions;

electronic control means responsive to said output signal from saidelectronic means to produce an electric operating pulse width signal;and

a fuel supply metering device which is actuated by said operating pulsewidth signal from said electronic control means to meter the flow offuel being supplied into said mixing means through said auxiliary fuelsupply passageway from said fuel supply reservoir.

20. In a carburetor as claimed in claim 19, said electronic computingmeans comprising at least one function generator responsive to at leastone of said electric signals representing said engine operatingconditions to produce at least one electronic 21. In a carburetor asclaimed in claim 20, said electronic control means comprising acomparator responsive to said electric output signal from said summingmeans to produce an electric pulse width signal, and amplifier foramplifying said pulse width a signal to produce said operating pulsewidth signal to be fed into said air-fuel mixture supply control system.

22. In a carburetor as claimed in claim 19, said fuel supply meteringdevice comprising a fuel flow control valve assembly which isoperatively disposed in said auxiliary fuel supply passageway formetering fuel passing therethrough, and an electric actuating device foractuating said fuel flow control valve assembly in response to saidoperating pulse width signal from said electronic means.

23. In a carburetor as claimed in claim 22, said electric actuatingdevice comprising a stationary core forming a housing which is providedwith a pair of solenoid coils, and a rockably movable core which isconnected at one end to said housing and the other end of which isrockably actuated by a magnetic force induced in said solenoid coils bysaid electric operating pulse width signal from said electronic controlmeans.

24. In a carburetor as claimed in claim 23, said flow control meansoperatively disposed in said auxiliary fuel supply passageway comprisinga flow control valve assembly which is operatively connected to andactuated by said other end of said movable core of said electricactuating device to meter the amount of fuel being supplied into saidmixing means through said auxiliary fuel supply passageway from saidfuel supply reservoir in response to said operating pulse width signalfrom said electronic control means.

1. In a carburetor for an internal combustion engine having air and fuelsupplying means which include mixing means for mixing air and fuel, atleast one air supply passageway and a main fuel supply passageway forsupplying air and fuel respectively into said mixing means, said atleast one air supply passageway being in communication with the ambientatmosphere, a fuel supply reservoir for supplying fuel into said mainfuel supply passageway, a flow control means operatively disposed insaid main fuel supply passageway, an air-fuel mixture supply passagewayfor supplying air-fuel mixture from said mixing means into an inductionpassage of said carburetor, throttling means operatively disposed insaid induction passage for controlling the amount of said air-fuelmixture being supplied into said engine, an auxiliary fuel supplypassageway bypassing said flow control means of said main fuel supplypassageway, flow control means operatively disposed in said auxiliaryfuel supply passageway, and an Air bleed jet mounted on said carburetorand communicating between the ambient atmosphere and said air and fuelsupplying means; an air-fuel mixture supply control system whichcomprises: electronic computing means responsive to at least one ofelectric signals representing prevailing values of engine operatingconditions including engine speed, engine temperature, throttle openingand atmospheric pressure to produce an electric output signalrepresenting an optimum airfuel ratio of said air-fuel mixture andcorresponding at all times to prevailing engine operating conditions;electronic control means responsive to said output signal from saidelectronic computing means to produce an electric operating signal; andan air supply metering device which is actuated by said operating signalfrom said electronic control means to meter a flow of air being passedthrough said air supply passageway from the ambient atmosphere.
 2. In acarburetor as claimed in claim 1, said electronic computing meanscomprising at least one function generator responsive to at least one ofsaid electric signals representing said engine operating conditions toproduce at least one electronic functional signal therefrom, and summingmeans responsive to said at least one functional signal to produce saidelectric output signal representing said optimum value of the air-fuelratio of said air-fuel mixture.
 3. In a carburetor as claimed in claim2, said electronic control means comprising an amplifier for amplifyingsaid electric output signal from said summing means to produce saidelectric operating signal to be fed into said air-fuel mixture supplycontrol system.
 4. In a carburetor as claimed in claim 1, said airsupplying metering device comprising an air flow control valve assemblywhich is operatively disposed over an opening of said air bleed jet formetering the amount of air being passed into said air supply passageway,and an electric actuating device for actuating said air flow controlvalve assembly in response to said operating signal from said electroniccontrol means.
 5. In a carburetor as claimed in claim 4, said electricactuating device comprising a stationary core forming a housing which ismounted on said carburetor and is provided with a pair of solenoid coilstherein, and a rockable movable core which is rockably connected at oneend to said housing and the other end of which is rockably moved in orout of said opening of said air bleed jet in response to a magneticforce induced in said solenoid coils.
 6. In a carburetor as claimed inclaim 5, said air flow control valve assembly comprising a valve needlewith a tapered end which projects into said opening of said air bleedjet and is fixedly attached to said other end of said movable core, saidtapered end being capable of varying the effective cross-sectional areaof said opening of said air bleed jet to thereby meter the amount of airbeing supplied into said air supply passageway from the ambientatmosphere.
 7. In a carburetor for an internal combustion engine havingair and fuel supplying means which include mixing means for mixing airand fuel, at least one air supply passageway and a main fuel supplypassageway for supplying air and fuel respectively into said mixingmeans, said at least one air supply passageway being in communicationwith the ambient atmosphere, a fuel supply reservoir for supplying fuelinto said main fuel passageway, flow control means operatively disposedin said main fuel supply passageway, an air-fuel mixture supplypassageway for supplying air-fuel mixture from said mixing means into aninduction passage of said carburetor, throttling means operativelydisposed in said induction passageway for controlling the amount of saidair-fuel mixture being supplied into said engine, an auxiliary fuelsupply passageway bypassing said flow control means of said main fuelsupply passageway, flow control means operatively disposed in saidauxiliary fuel supply passageway, and an air bleed jet mounted on saidcarburetor and communicating between the ambient atmosphere and said airand fuel supplying means; an air-fuel mixture supply control systemwhich comprises: electronic computing means responsive to at least oneof electric signals representing prevailing values of engine operatingconditions including engine speed, engine temperature, throttle openingand atmospheric pressure to produce an electric output signalrepresenting an optimum air-fuel ratio of said air-fuel mixturecorresponding at all times to prevailing engine operating conditions;electronic control means responsive to said output signal from saidelectronic computing means to produce an electric operating signal; anda fuel supply metering device which is actuated by said operating signalfrom said electronic control means to meter a flow of fuel beingsupplied into said air and fuel mixing means through said auxiliary fuelsupply passageway from said fuel supply reservoir.
 8. In a carburetor asclaimed in claim 7, said electronic computing means comprising at leastone function generator responsive to at least one of said electricsignals representing said engine operating conditions to produce atleast one electronic functional signal therefrom, and summing meansresponsive to said at least one functional signal to produce saidelectric output signal representing said optimum value of the air-fuelratio of said air-fuel mixture.
 9. In a carburetor as claimed in claim8, said electronic control means comprising an amplifier for amplifyingsaid electric output signal from said summing means to produce electricoperating signal to be fed into said air-fuel mixture supply controlsystem.
 10. In a carburetor as claimed in claim 8, said fuel supplymetering device comprising a fuel flow control valve assembly which isoperatively disposed in said auxiliary fuel supply passageway, and anelectric actuating device for a actuating said fuel flow control valveassembly in response to said operating signal from said electroniccontrol means for metering the amount of fuel being supplied into saidair and fuel mixing means through said auxiliary fuel supply passagewayfrom said fuel supply reservoir.
 11. In a carburetor as claimed in claim10, said electric actuating device comprising a stationary core forminga housing which is provided with a pair of solenoid coils therein, and arockable movable core which is rockably connected at one end to saidhousing and the other end of which is rockably actuated by a magneticforce induced in said solenoid coils by said electric operating signalfrom said electronic control means.
 12. In a carburetor as clained inclaim 11, said fuel flow control valve assembly being operativelydisposed in said auxiliary fuel supply passageway and operativelyconnected to and actuated by said other end of said movable core of saidelectric actuating device to meter the amount of fuel being suppliedinto said air and fuel mixing means through said auxiliary fuel supplypassageway from said fuel supply reservoir in response to said electricoperating signal from said electronic control means.
 13. In a carburetorfor an internal combustion engine having air and fuel supplying meanswhich include mixing means for mixing air and fuel, at least one airsupply passageway and a main fuel supply passageway for supplying airand fuel respectively into said mixing means, said at least one airsupply passageway being in communication with the ambient atmosphere, afuel supply reservoir for supplying fuel into said main fuel supplypassageway, an air-fuel mixture supply passageway for supplying air-fuelmixture from said mixing means into an induction passage of saidcarburetor, throttling means operatively disposed in said inductionpassageway for controlling the amount of said air-fuel mixture beingsupplied into said engine, an air bleed jet communicating between theambient atmosphere and said air and fuel supplying means, flow cOntrolmeans operatively disposed in said main fuel supply passageway, anauxiliary fuel supply passageway bypassing said flow control means ofsaid main fuel supply passageway, and a flow control means operativelydisposed in said auxiliary fuel supply passageway; an air-fuel mixturesupply control system which comprises: electronic computing meansresponsive to an electric dither signal and at least one of electricsignals representing prevailing values of engine operating conditionsincluding engine speed, engine temperature, throttle opening andatmospheric pressure to produce an electric output signal representingan optimum air-fuel ratio of said air-fuel mixture and corresponding atall times to prevailing engine operating conditions; electronic controlmeans responsive to said output signal from said electronic computingmeans to produce an electric operating pulse width signal; and an airsupply metering device which is actuated by said operating pulse widthsignal from said electronic control means to meter the flow of airpassing through said at least one air supply passageway from the ambientatmosphere.
 14. In a carburetor as claimed in claim 13, said electroniccomputing means comprising at least one function generator responsive toat least one of said electric signals representing said engine operatingconditions to produce at least one electronic functional signaltherefrom, and summing means responsive to said at least one functionalsignal and said dither signal to produce said electric output signalrepresenting said optimum air-fuel ratio of said air-fuel mixture. 15.In a carburetor as claimed in claim 14, said electronic control meanscomprising a comparator responsive to said electric output signal fromsaid summing means to produce an electric pulse width signal, and anamplifier for amplifying said pulse width signal to produce saidoperating pulse width signal to be fed into said air-fuel mixture supplycontrol system.
 16. In a carburetor as claimed in claim 13, said airsupply metering device comprising an air flow control valve assemblywhich is operatively disposed over an opening of said air bleed jet formetering the amount of air being passed into said air supply passageway,and an electric actuating device for actuating said air flow controlvalve assembly in response to said operating pulse width signal fromsaid electronic control means.
 17. In a carburetor as claimed in claim16, said electric actuating device comprising a stationary core forminga housing which is mounted on said carburetor and is provided with apair of solenoid coils therein, and a rockable movable core which isrockably connected at one end to said housing and the other end of whichis rockably moved in or out of said opening of said air bleed jet inresponse to a magnetic force induced in said solenoid coils.
 18. In acarburetor as claimed in claim 17, said air flow control valve assemblycomprising a valve needle with a tapered end which projects into saidopening of said air bleed jet and is fixedly attached to said other endof said movable core, said tapered end being capable of opening andclosing said opening of said air bleed jet to meter the amount of airpassing into said air supply passageway from the ambient atmosphere. 19.In a carburetor for an internal combustion engine having air and fuelsupplying means which include mixing means for mixing air and fuel, atleast one air supply passageway and a main fuel supply passageway forsupplying air and fuel respectively into said mixing means, said atleast one air supply passageway being in communication with the ambientatmosphere, a fuel supply reservoir for supplying fuel into said mainfuel supply passageway, flow control means operatively disposed in saidmain fuel supply passageway, an air-fuel mixture supply passageway forsupplying air-fuel mixture from said mixing means into an inductionpassage of said carburetor, throttling means operatively disposed iNsaid induction passage for controlling the amount of said air-fuelmixture being supplied into said engine, an auxiliary fuel supplypassageway bypassing said flow control means of said main fuel supplypassageway, flow control means operatively disposed in said auxiliaryfuel supply passageway, and an air bleed jet mounted on said carburetorand communicating between the ambient atmosphere and said air and fuelsupplying means; an air-fuel mixture supply control system whichcomprises: electronic computing means responsive to an electric dithersignal and at least one of electric signal representing prevailingvalues of engine operating conditions including engine speed, enginetemperature, throttle opening and atmospheric pressure to produce anelectric output signal representing an optimum air-fuel ratio of saidair-fuel mixture and corresponding at all times to prevailing engineoperating conditions; electronic control means responsive to said outputsignal from said electronic means to produce an electric operating pulsewidth signal; and a fuel supply metering device which is actuated bysaid operating pulse width signal from said electronic control means tometer the flow of fuel being supplied into said mixing means throughsaid auxiliary fuel supply passageway from said fuel supply reservoir.20. In a carburetor as claimed in claim 19, said electronic computingmeans comprising at least one function generator responsive to at leastone of said electric signals representing said engine operatingconditions to produce at least one electronic
 21. In a carburetor asclaimed in claim 20, said electronic control means comprising acomparator responsive to said electric output signal from said summingmeans to produce an electric pulse width signal, and amplifier foramplifying said pulse width a signal to produce said operating pulsewidth signal to be fed into said air-fuel mixture supply control system.22. In a carburetor as claimed in claim 19, said fuel supply meteringdevice comprising a fuel flow control valve assembly which isoperatively disposed in said auxiliary fuel supply passageway formetering fuel passing therethrough, and an electric actuating device foractuating said fuel flow control valve assembly in response to saidoperating pulse width signal from said electronic means.
 23. In acarburetor as claimed in claim 22, said electric actuating devicecomprising a stationary core forming a housing which is provided with apair of solenoid coils, and a rockably movable core which is connectedat one end to said housing and the other end of which is rockablyactuated by a magnetic force induced in said solenoid coils by saidelectric operating pulse width signal from said electronic controlmeans.
 24. In a carburetor as claimed in claim 23, said flow controlmeans operatively disposed in said auxiliary fuel supply passagewaycomprising a flow control valve assembly which is operatively connectedto and actuated by said other end of said movable core of said electricactuating device to meter the amount of fuel being supplied into saidmixing means through said auxiliary fuel supply passageway from saidfuel supply reservoir in response to said operating pulse width signalfrom said electronic control means.